An obtuse triangle is a triangle v one interior angle measure greater than 90 degrees. In geometry, triangles are considered as 2D closed figures with 3 sides that the exact same or various lengths and three angles with the exact same or different measurements. Based upon the length, angles, and also properties, there are 6 kinds of triangles the we discover in geometry i.e. Scalene triangle, best triangle, acute triangle, obtuse triangle, isosceles triangle, and also equilateral triangle.

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If one of the inner angles that the triangle is much more than 90°, then the triangle is called the obtuse-angled triangle. Let's learn much more about obtuse triangles, their properties, the formulas required, and solve a few examples to know the ide better.

1.What Is an Obtuse Triangle?
2.Obtuse Angled Triangle Formula
3.Obtuse Angled Triangle Properties
4.FAQs on Obtuse Triangles

What Is one Obtuse Triangle?

An obtuse-angled triangle or obtuse triangle is a form of triangle whose one of the vertex angles is bigger than 90°. One obtuse-angled triangle has actually one of its vertex angles as obtuse and other angle as acute angle i.e. If one of the angle measure an ext than 90°, climate the sum of the other two angle is much less than 90°. The side opposite come the obtuse edge is taken into consideration the longest. Because that example, in a triangle ABC, three sides the a triangle measure up a, b, and also c, c gift the longest next of the triangle as it is the opposite side to the obtuse angle. Hence, the triangle is one obtuse-angled triangle whereby a2 + b2 2

An obtuse-angled triangle deserve to be a scalene triangle or isosceles triangle but will never be equilateral since an equilateral triangle has actually equal sides and also angles wherein each angle actions 60°. Similarly, a triangle cannot be both an obtuse and also a right-angled triangle since the appropriate triangle has one edge of 90° and the various other two angles space acute. Therefore, a right-angle triangle cannot be one obtuse triangle and also vice versa. Centroid and incenter lie in ~ the obtuse-angled triangle when circumcenter and also orthocenter lie exterior the triangle.

The triangle below has one angle higher than 90°. Therefore, that is dubbed an obtuse-angled triangle or simply an obtuse triangle.


Obtuse Angled Triangle Formula

There are different formulas to calculation the perimeter and also the area of an obtuse triangle. Let's find out each the the recipe in detail.

Obtuse Triangle Perimeter

The perimeter of an obtuse triangle is the sum of the actions of all its sides. Hence, the formula because that the perimeter of an obtuse-angled triangle is:

Perimeter of obtuse angled triangle = (a + b + c) units.

Area of Obtuse Triangle

To find the area of an obtuse triangle, a perpendicular heat is built outside the the triangle wherein the height is obtained. Because an obtuse triangle has actually a worth of one angle more than 90°. Once the height is obtained, us can discover the area of one obtuse triangle by using the formula mentioned below.

In the offered obtuse triangle ΔABC, we know that a triangle has actually three altitudes indigenous the 3 vertices to the opposite sides. The altitude or the elevation from the acute angles of one obtuse triangle lies external the triangle. We expand the base together shown and determine the height of the obtuse triangle


Area that ΔABC = 1/2 × h × b wherein BC is the base, and h is the elevation of the triangle.

Area of an Obtuse-Angled Triangle = 1/2 × base × Height

Obtuse Triangle Area by Heron's Formula

The area of an obtuse triangle can additionally be found by making use of Heron's formula. Consider the triangle ΔABC through the size of the sides a, b, and c.

Heron's formula to uncover the area of one obtuse triangle is: (sqrt s(s - a)(s - b)(s - c)), where, (a + b + c) is the perimeter that the triangle and S is the semi-perimeter which is given by (s): = (a + b + c)/2

Properties the Obtuse-Angled Triangles

Each triangle has its very own properties that define them. An obtuse triangle has actually four various properties. Let's check out what they are:

Property 1: The longest side of a triangle is the next opposite come the obtuse angle. Think about the ΔABC, next BC is the longest next which is opposite come the obtuse edge ∠A. Check out the image below for reference.


Property 2: A triangle have the right to only have one obtuse angle. We recognize that the angle of a triangle amount up to 180°. Think about the obtuse triangle displayed below. We can observe that one of the angle measures better than 90°, making it an obtuse angle. Because that instance, if one of the angle is 91°, the amount of the various other two angles will certainly be 89°. Hence, a triangle cannot have two obtuse angles since the amount of every the angles cannot exceed 180 degrees. Watch the image given listed below to understand the exact same with an illustration.


Property 3: The amount of the other two angles in an obtuse triangle is always smaller 보다 90°. We just learned that as soon as one that the angle is an obtuse angle, the other two angles include up to much less than 90°.


In the over triangle, ∠1 > 90°. We know that by angle sum property, the amount of the angle of a triangle is 180°. Therefore, ∠1 + ∠2 + ∠3 = 180° and ∠1 > 90°

Subtracting the above two, we have, ∠2 + ∠3 As checked out in the picture below:


Circumcenter (H), the median suggest from every the triangle vertices, lies exterior in one obtuse triangle. As viewed in the photo below:


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Example 2: uncover the height of the given obtuse-angled triangle who area = 60 in2 and base = 8 in.



Area of one obtuse-angled triangle = 1/2 × base × height. Therefore, the elevation of the obtuse triangle can be calculation by:

Height = (2 × Area)/base

Substituting the values, we get:

Height = (2 × 60)/8 = 15 inches

Therefore, the elevation of the provided obtuse triangle is 15 inches.

Example 3: deserve to sides measuring 3 inches, 4 inches, and 6 inches form an obtuse triangle?


The political parties of one obtuse triangle should satisfy the problem that the amount of the squares of any type of two political parties is lesser than the square the the third side.

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We know that

a = 3 in

b = 4 in

c = 6 in

Taking the squares the the sides, we get: a2 = 9, b2 = 16, and also c2 = 36

We understand that, a2 + b2 2

36 > (9 + 16)

The provided measures can kind the sides of an obtuse triangle. Therefore, 3 inches, 4 inches, and also 6 inches have the right to be the political parties of one obtuse triangle.